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I thought I'd share some information on my favourite Su-17 version , feel free to discuss, post questions etc in the comments!!
In 1972 the Sukhoi design bureau began work on another variant of the Su-17) it was known only by its in-house designation S-32MK "гибридный" or hybrid, this mated the wings of the Su-7BMK to the fuselage of the Su-17M. The aircraft first flew in February 1973 piloted by Vladimir Krechetov.
The only known photo of the S-32MK to exist in the west, note the large bomb load able to be carried. Also note how the gun blast plates are still installed but the twin NR-30 cannons are not.
The S-32MK's fuselage was taken from the new into production Su-17M line, for the S-32MK the uprated AL-21F-3 engine which provided more thrust compared to the standard Fitters then in production. During tests the performance of the Hybrid was better than the Su-17 then in service, the S-32 reached a height of 1800M compared to the 1500M compared to the production Su-17M.
The fitting of the Su-7BMK wing had positives and negatives, the removal of the complicated and heavy Su-17 swing wing system allowed for not only a lighter airframe but a Increase in the fuel capacity (400kg extra fuel) the removal of the swing wing also allowed for maintenance to be much easier. However a drawback of the wing was a return to the Su-7s high landing and takeoff speeds, poor agility at low speeds and a high stall speed. The test machine also had a 100mph higher top speed compared to the Su-17M due to all the weight saving.
A side view of the aircraft, again showing the large number of pylons, and highly swept wing.
The aircraft was planned to be armed with the standard twin NR-30, 30mm cannons in the wing roots with 80 rounds per gun, the standard six Su-7 pylons (two under each wing and two under the fuselage) were joined by two inner pylons from the standard Su-17 creating a total of eight pylons, two more compared to standard Su-17s, the weight saving allowed for the increase in weapons.
The soviet Airforce although interested in the design favoured the Mig-27 and Su-17M, therefore Sukhoi offered the jet on export. It was given the export name Su-20, Egypt was the first country to show interest in the new Sukhoi. However Egypt opted for the Su-17M as it had bad past experiences with the Su-7 and saw the swept wing Su-20 as a throwback to bad experiences, Syria also showed interest however they soon withdrew interest.
With the lack of interest by both Soviet and overseas airforces finally meant to a scrapping of the project and in mid 1975 the aircraft was withdrawn from tests and sent to Tula and used as a mechanic practise aircraft until the 1990s, the airframes existence after 1990 is unknown however it is rumoured that it was more than likely scrapped.
Artwork of the S-32MK during tests. The 17 red was only applied for later flights.